If someone is going to truly develop an app for waterskiing please make it work with a gimble. Modern gimbles have the ability to track a person or object, keeping that selected item in focus, in the middle of the screen and eliminating any camera shake. The current limitations (with my DJI) are only allowing for the 1x lens on iphone, need to manually select the focus object each time recording it stopped and no speed based recording.
To me, the ultimate solution is to have a gimble mounted to a skidoc. The ski doc will keep the phone generally in line with the skier then the gimble can move to keep the skier centered with higher zoom and eliminate any camera shake. It would be great if you could select the skier as the focus object prior to the start of their set and then have speed based recording. I may be dreaming, but this seems possible and would result in high quality footage that could be used for in-depth video coaching.